Mechanism of Silver(I) Oxide Formation on Polycrystalline Silver Electrodes in 8 M KOH Solution

The kinetics of silver(I) oxide formation on polycrystalline silver electrodes in 8 M KOH solution was investigated by cyclic voltammetry, potentiostatic and galvanostatic techniques as well as the morphology of the silver(I) oxide structures by scanning electron microscopy. Potentiostatic investigations revealed unambiguously that the silver(I) oxide may be nucleated in the second stage as well as in the third stage of silver(I) oxide formation. Cyclic voltammograms showed that the second peak current could be larger than the third peak current with repetitive cycling. Microscopic examinations provided undoubted evidence that electrodissolution, nucleation, three-dimensional (3D) growth, and Ostwald ripening processes are involved in the initial stage of silver(I) oxide formation. In addition, it was found that two types of silver(I) oxide morphologies were formed by progressive nucleation and instantaneous nucleation process. On the basis of the experimental results, a model of silver(I) oxide formation involving electrodissolution, progressive nucleation, instantaneous nucleation, and 3D growth processes is proposed.